Metal nitrides are powders generally prepared from high temperature treatment of a source of metal and a source of nitrogen. Preparation of metal nitride films is usually carried out by chemical vapor deposition methods which require expensive instrumentation. If films are to be localized on the small area of a substrate, the rest of the area needs to be protected which adds to the cost of preparation of localized films. Clearly, new methods need to be developed which are convenient and economically acceptable. It would be desirable if localized coatings of metal nitrides could be produced by a method involving photolytic decomposition which would allow only the desired area of a substrate which has been covered with a metal nitride precursor to be converted to the metal nitride. According to such a process, a substrate could be covered with a metal nitride precursor and then the desired area could be irradiated with a suitable light which would result in the decomposition of the precursor. The undecomposed precursor could subsequently be removed and then the substrate processed further to convert the decomposed precursor to a metal nitride coating.
Narula and Maricq, the present inventors, in an article entitled "1.064 .mu.m Multiphoton Laser-induced Fluorescence and Dissociation of Tetrakis-(dimethylamino) Titanium(IV)", Chemical Physics Letters, Volume 198, number 3, 6, December, 1991, disclose that titanium amide when subjected to a particular laser light decomposes primarily to an insoluble residue metal amide oligomer and dimethylamine. In articles entitled "Laser Induced Decomposition of Precursors Containing M-N Bonds for the Preparation of Metal-Nitride Preceramics, Powders and Coatings", Am. Chem. Soc. Pol. Div. 32,499 (1991), and "Preparation of Composite Particles by Pulsed Nd-TAG Laser Decomposition of [(CH.sub.3).sub.2 N].sub.4 Ti to TiN Coat Al.sub.2 O.sub.3, TiO.sub.2 O.sub.2 Si.sub.3 N.sub.4 Powders" J. Am Ceram. for. (1993) 2727 Narula and Maricq disclose that after subjecting the titanium amide to photolytic decomposition by means of a laser, the resulting material can be pyrolyticly decomposed to form titanium nitride. Both of these article disclose that materials similar to the titanium amide, i.e., boron amide and silicon amide, in contrast, were found unexpectedly to not decompose when exposed to the laser.